Determination of the content of a mineral in ores and the like



NW. 22, 1949 R. c. Q. WllG 2,489,066

DETERMINATION OF THE CONTENT OF A MINERAL IN ORES AND THE LIKE FiledOct. 3, 1945 2 Sheets-Sheet l Nov. 22, 1949 c. a, [G 2,489,066

R DETERMINATION OF C N EN F A MINERAL IN OH'ES AND E L E Filed Oct. 3,1945 2 Sheets-Sheet 2 Patented Nov. 22, 1949 DETERIVIINATION'OF THECONTENT OF A MINERAL IN ORES AND THE LIKE Rasrnfis ChristianQstraat'Wiig, Svarstad, Norway Application October 3, 1945, Serial No.620,072 In Norway September 29, 1941 Section 1, Public Law 690, August8, 1946 Patent expires September 29, 1961 2 Claims. 1

The present invention relates to a method and a device by which it ispossible to quickly and readily determine the mineral content of ores,for example the respective Fe or iron, content of ore concentrates, andwaste samples, from concentration machines. The invention issubstantially characterized by the fact that samples of the-ore areinserted as acore in a magnetic field, and that the increase of themagnetic field thus obtained is measured and gives a measure of themineral content.

It is of particular importance to undertake such measurement whendealing with magnetic concentration of iron ore sources in which iron isalso present in slightly magnetic or non-magnetic condition. This factwill appear from the following statement.

Magnetite sources almost always contain some iron in slightly magneticor non-magnetic condition, in the form of FezOa or ferric oxide, forexample. When the Fe content of the source is too low to be utilized itmust be concentrated. This is usually done by magnetic concentration.The concentration machine works on the principle. that the magneticmaterial of the crushed ore is attracted by magnets and is transportedto one place, while the non-magnetic material leaves as waste. Thereforeit is necessary that as. little as possible of the material thatcontains iron, which can be attracted by magnets, be lost with theWaste, and thus it is necessary to control the waste through analyses.In the known methods it. has been necessary to determine the Fe contentchemically, perhaps [preferabl through so-called l-ICl or hydrochloricacid analyses. As mentioned above, the magnetite seldom occurs by itselfand the ore source usually includes hematite or other more or lessslightly magnetic iron compounds together with the magnetite. Even ifthe former constitutes a small part of the iron quantity in the oresource it might, however, constitute an essential part of the wasteduring the difierent concentration stages. In determining the ironcontent of the waste material through I-ICl-analyses, in order to usethe same as a basis for judging the working condition of the machines,the size of the iron loss is indicated, but the analyses give anincorrect view of the working capacity and condition oflthe. machines.As a matter of fact, the H01- analyses indicate the presence ofnon-magnetic iron which is soluble in hydrochloric acid. According tothe mode of operation of the machines the said iron must be separatedtogether with thewaste. The misjudgment cause-d hereby is clear from thefollowing example:

A raw ore contains Fe, 0.5-1% of which is in the form of FezOa. This oreis of course concentrated magnetically. During the first concentrationstage about 20 percent by weight is over, the analyses will show varyingquantities of Fe, between 2.5 and 5%, according to the quantity ofhematite in the ore supplied. Thus no HCl-analyses indicating betweenabout 1 and 5.5% Fe will to a certainty indicate whether the Fe-contentof the waste is due to the fact that the concentration machine isworking improperly or whether the supplied ore has contained hematite orother iron compounds soluble in hydrochloric acid. Moreover, it israther impossible to correct the result by a calculation ofprobabilities because the hematite content might vary from one place tothe other i the mine. Also,

. since the material to be concentrated is not sufficiently mixed beforedistribution to the various systems in the concentration plant anycomparison between the material leaving the various machines would be ofno avail. It is generally known that the exact difference between thetotal Fe content in the waste and the Fe content in the form of F6304 or'ferro-soferric oxide, must be obtained. The known methods for thisdetermination have either taken too long a time or have been sotroublesome that it has been extremely difiicult to test more than avery few samples a day. In order to obtain the best results inconcentration it is of the greatest importance that the Fe3O4 content ofthe waste and of the concentrate be determined as quickly as possibleboth during the daily operation as well as during tests conducted toimprove results earlier obtained. By the present method and apparatusany person, without chemical training, will be able to immediatelyestablish the working condition of the concentration machines. Furtheranyone can make hundreds of tests a day with a single apparatus andwithout the use of chemicals.

There are also other occasions when iron of different magneticproperties is present in various compounds. It is usual to employmachines, the mode or operation of which is based on the magneticproperties of the magnetite when the iron occurs as magnetite. This isusual whether the magnetite occurs as ore worth breaking or as animpurity in other ores or products worth breaking. Also in this case aquick and reliable control of the machines is of the greatestimportance. The concentration of titanium ore may be mentioned as anexample. Magnetite as well as ilmenite may here occur in breakablequantities but they must be separated from one another. In theconcentration of the magnetite the presence of ilmenite inconveniencesthe control of the machine. The slightly magnetic ilmenite leaves themachine with the waste material containing the magnetite and thus givesthe waste an iron content which is not characteristic for the workingcondition of the machine, unless checked by undertaking other analyses.In the concentration of ilmenite the use of the present apparatusenhances the control of the machines. If, in operation, Fe occurs in theform of F8203 the present method is not only much quicker than thechemical one but it also provides a safer basis for judging themachines,

The susceptibility of magnetite is constant within wide limits in powderform and therefore a sample containing magnetite together with othernon-magnetic or slightly magnetic compounds will change itssusceptibility in relation to the concentration of magnetite. Tests haveproved that exact measurements can be made very quickly and that thesame are only dependent on the magnetic properties of the samples andtherefore practically independent of the size and compaction of thegrains.

In the determination of a magnetite content for example. the method iscarried into efiect in the following way. In making exact determinationsa dried sample is placed in a suitable container and packedsufficiently. The size of the sample is without importance. Theprincipal thing is that the container be more than half filled.Thereafter the container is inserted as a core in a magnet field in anapparatus which by deflection of a pointer directly indicates the per-'centage of Fe in the form of magnetite. A single person can make thewhole determination in a few seconds.

The total time required for this determination is only dependent on thetime required for the sample to dry. In the control of concentrationmachines it is often unnecessary to make this ex act determination, andthus if the sample is in a wet state it is only necessary to mix itafter it has had an opportunity of sinking. This is of great importancewhen it is necessary to quickly control a concentration machine.

As mentioned above, magnetite occurs as impurity, and it might be ofinterest to be able to quickly determine the quantity of this impurityin a slightly magnetic or nonmagnetic material,

in ilmenite or in raw materials used by the glass industry for example.

Having generally set forth the invention the same is illustrated on theaccompanying drawings in which:

Figs. 1 and 2 are diagrammatic side and top views, respectively, of oneembodiment of the invention,

Fig. 3 illustrates a modification thereof,

Figs. 4 and 5 are diagrammatic top and side views of anothermodification, and

Figs. 6 to 10 illustrate still further modifications.

In Figs. 1 and 2 iron members 4 and 5 are placed symmetrically about themovable coil I of a moving coil instrument. These members are made oflaminated iron and have a small remanence. The hollow coils 2 and 3 areconnected in such a way that the magnetic fields obtained, when thecurrent is closed through them, counteract one another so that nomagnetic lines of force cross the magnetic lines of force generated bythe movable coil I when the current has been closed through the same.The pointer of the movable coil instrument will then point to zero onthe scale 6. Thus when a sample containing iron ore in the form ofmagnetite is inserted in the space of the coil 2, the pointer will makea deflection which can be read on the scale 6 in percentage by weight ofFe. Also the iron armature 9 can by means of rack 8 be pushed into thecoil 3 until the pointer points to zero again. The percentage by weightof Fe can then be read on the scale 1 which is empirically graduated.

In measuring apparatus which are to register very small iron contents acompensator in the form of a permanent magnet It! should be utilized.This magnet should be mounted in such a way that it is adjustable andcan be adjusted so that its magnetic field counteracts the residualmagnetism acting on the coil In Fig. 3 a somewhat modified embodiment ofthe invention is shown wherein the movable coil is mounted in a gapbetween the ends of the arm member 5 so that the scale 6 can be disposedat the side of the device. The compensation device lO used in the formshown in Figs. 1 and 2 may be used in this arrangement.

In the modification shown in Figs. 4 and 5 the magnetic circuit of asolenoid A having a core of air has been closed through the iron partsof the apparatus, namely, the solenoid cylinders and the iron arms a.

The magnetic field which is indicated by the arrows F is generatedeither by a permanent magnet or an electromagnet, and is chosen as largeas and directed opposite to the field generated by the solenoid A. Thelines of force in the moving coil instrument B are not in this casecrossed by any flux and the pointer of the instrument adjusts itself tozero.

By filling the core of the solenoid A with a sample containing permeablematerial there is generated a field which causes the pointer of themoving coil instrument to be deflected.

' An adjustable magnet O is mounted in such a way that its field cancounteract the action of the residual magnetism of the iron constructionrelative to the moving coil instrument B.

When the sample is allowed to sink it becomes uneven because thematerial settles in the form of layers. This can have a disturbingeifect when the sample is not mixed and the lines of force extendthrough the sample in the longitudinal [6 direction. Therefore, theembodiment shown in Fig. 6 is better because the lines of force extendthrough the sample in the transverse direction since the coil isdisposed vertically.

When alternating current of suitable frequency is used the bridgeconnection shown in Fig. 7 can be employed.

The galvanometer G is provided with a rectifier. The sample is insertedin the coil S. The movable contact A which is adjusted along the bridgeso that it becomes without current, moves along 1 an empiricallygraduated scale, and the percent of Fe can be read directly when thegalvanometer G is pointing to zero.

In Fig. 8 is shown a transformer with two windings, alternating currentbeing sent through its primary winding and the secondary tension ismeasured.

The secondary tension becomes dependent on the sample placed in thetransformer core. As the tension change becomes small when it is thequestion of poor samples one should compensate the secondary tensionwhich is obtained with air only as transformer core so that themeasuring instrument is pointing to zero prior to inserting the sample.This has proved to be difficult if one does not use a rectifier andcompensates with continuous-current, as shown in Fig. 9.

In the modification shown in Fig. 10 exactly equal transformers I and IIand rectifiers L1 and L2 are utilized. The galvanometer G is a movingcoil instrument which is graduated on both sides of the zero point. Whenthe current is closed through the two primary windings the galvanometerG will point to zero. In the same way it will point to zero when sampleswith the same magnetic properties are inserted in the transformers I andII. If one of the said samples is known the other is thus determined.Therefore, standard samples can be placed in the core II to determinethe samples inserted in the core I.

In order to easily and quickly read the percentage directly by weight ofFe, an iron armature is mounted for insertion as a core in thetransformer II. This insertion can be made with a rack and a toothedwheel, similar to the arrangement of Fig. 1, in such a Way that one canread the position of the iron armature in the coil on a scale. Thisscale can be graduated empirically in percent of Fe, and in this way onecan thus determine the samples inserted in the transformer I.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In apparatus for determining the mineral content of ore, two spacedhollow coils connected to provide oposed magnetic fields, at least oneof said coils having an open internal space for freely accommodating thematerial to be tested, a magnetic member bridging ends of the coils, amagnetic member bridging the other ends of the coils, a movable coilmounted between said members adapted to be influenced by lines of fiuxbetween said members, a pointer carried by said movable coil, andmagnetic means for counteracting residual magnetism acting on said coil.

2. In apparatus for determining the mineral content of ore, two spacedhollow coils connected to provide opposed magnetic fields, at least oneof said coils having an open internal space for freely accommodating thematerial to be tested, a magnetic member bridging ends of the coils, amagnetic member bridging the other ends of the coils, a movable coilmounted between said members adapted to be influenced by lines of fluxbetween said members, a pointer carried by said movable coil, and meansincluding an indicator for varying the permeability of one of saidhollow coils.

RAsMfJs CHRISTIAN osTRAAT WIIG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,640,524 Augustine Aug. .30,1927 1,682,435 Spooner Aug. 28, 1928 1,952,185 Smith Mar. 27, 19341,966,984 Lichtenberger et a1. July 17, 1934 1,989,037 Brown Jan. 22,1935 2,228,293 Wurzbach Jan. 14, 1941 FOREIGN PATENTS Number CountryDate 72,004 Norway Apr. 28, 1947

